The objective of this program is the development of a new prosthesis for the replacement of vessels smaller than 6 mm diameter. The prosthesis employs a polyurethane fibril microporous textured surface at the blood interface designed to generate a pseudoneointima (PNI) from blood flowing over the surface. While similar in that respect to conventional dacron or expanded teflon grafts, which also rely on PNI generation for blood compatibility, the new microporous surface is applied on a substrate whose compliance is approximately matched to a comparably sized artery. The textured surface will also be applied to the exterior of the graft to promote tissue attachment and maintain the compliance of the graft in a physiologic range following healing of the perigraft tissues. It is postulated that compliance mismatch is at least in part responsible for the intimal hyperplasia that is frequently seen at the anastomotic sites with conventional prostheses. By lessening intimal hyperplasia, improved patency may result. To evaluate the new prosthesis, a series of 6 grafts are to be implanted in the carotid arteries of adult dogs after the structural integrity of the new surface has been demonstrated in vitro. Non-compliant grafts will be implanted contralaterally as a control. After 8 weeks, the animals are to be sacrificed. The compliance of the graft is to be measured in situ, and the implants removed for histopathologic analysis. The composition, structure, and thickness of the PNI from both groups will be compared, and the anastomotic sites will be examined for evidence of diminished intimal hyperplasia resulting from the new prosthesis design.